<h1 id="chapter-1"><a class="header" href="#chapter-1">Chapter 1</a></h1>
<pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let x = 2021;
<span class="boring">}</span></code></pre>
<pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let x = 2021;
<span class="boring">}</span></code></pre>
<pre class="playground"><code class="language-rust edition2024"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let x = 2024;
<span class="boring">}</span></code></pre>